Lithographic printing foil



y 1965 F. w. VON MEISTER ETAL 3,183,832

LITHOGRAPHIC PRINTING FOIL FIGJ FIG.2

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INVENTORS FREDERICK W. van MEISTER ATTORNEYS United States Patent 3,183,832 LITHOGRAPHIC PRINTHNG FOIL Frederick W. von Meister, Peapack, N "L, and Edmund B.

Fritz, Yaiesville, (Ionm, assignors to Azoplate Corporation, a corporation of New Jersey Filed Feb. 1, 1960, Ser. No. 5,751 4 tClaims. (Cl. 101-1491) This invention relates to printing plates or masters suitable for use in the lithographic offset process and, more particularly, the invention is concerned with thin plates or masters adapted for use in small size duplicating machines of the litho offset type.

In the process of offset printing on duplicator type presses, as well as professional presses, the plates carrying the printing image consist of a suitable support material, generally paper or aluminum or other metal foil or a combination of both. These plates or masters may either be pretreated to permit direct imaging by typewriter, pencil, pen or other means, or may be sensitized by the user to reproduce photographic images or may be presensitized by the manufacturer also for the purpose of reproducing printed images by photochemical means. Such plates or masters may also be coated with photoconductive layers which will permit imaging by means of electrostatic photographic methods.

By far, the greatest portion of the cost of manufacture of such printing plates resides in the expense for the raw material forming the support. This is of particular importance with metal plates. Of the metals used, aluminum is the preferred metal. In practice, plate thicknesses run from 0.0035 inch to 0.0075 inch and higher. Attempts to use aluminum foils thinner than about 0.0035 inchto reduce the costs have only been successful when very thin aluminum foils,such as 0.0005 inch laminated to a suitable paper sheet, have been used. In general, however, such thin metal foils are frequently damaged during processing by kinking or otherwise, even before their installation on the press. Additionally, the frictional forces of the dampener and of the ink rollers exerted on the plate surface during the printing process tend to tear plates of such thin gauges from the attaching devices of the press cylinder.

It has been suggested to use printing foils of which both surfaces have been treated for imaging or presensitized and thereby are adapted for the production of one reproducible image on each side. With a thickness of 0.004 of an inch, two useful printing surfaces are obtained instead of one. It is to be understood that the term useful surface, used hereinafter, refers to the surface of a printing foil which has been either presensitized or processed in any other conventional manner so that a reproducible image can be formed thereon. This may include a special preparation of the foil followed by subsequently applying the image thereon by typing or drawing.

This present invention is concerned with further reducing the costs and the weight of printing foils by providing an increased number of useful surfaces without increasing the weight of material used, the space required for storage and the expenditures for raw material.

The basic concept of this invention resides in the provision of a pair of printing foils which are attached to each other alongside of one common edge to form a double printing foil to be attached to a printing press cylinder in a conventional manner, but having up to four useful surfaces. Thereby one foil reinforces the other so that the thickness of each of the foils can be less than that of conventional, single foils. A dual unit so defined is readily obtained by starting from a double-sized sheet and folding it over along a center fold. The sheet support, generally of aluminum or paper, may have been pretreated to impart a direct image printing surface, or may have been Patented May 18, 1965 previously sensitized in a customary manner, either on one or one both sides. The twin printing foil so obtained resembles a folder and includes four surfaces, all of which may be processed as set forth above. By forming marginal rows of perforations in a conventional manner, the double printing plate of this invention is attached to the cylinder of an offset printing press whereby the perforations cooperate with the clamps or hooks with which this type of press is provided. Generally, at least two, and preferably all four sides of the double foil have been processed and, when clamping the folded foil to the cylinder of the press, the surface facing outwardly will operate as the master for the copies to be made. By attaching the double foil in a reversed position, the other outer surface becomes that which faces the offset cylinder. In order to print copies from .one of the surfaces, which are initially inside the folded double sheet, the two foils are readily unfolded and bent in the reversed direction whereby the inner surfaces become the outer ones, and vice-versa.

During operation, and since they are attached to each other and to the cylinder, each printing foil reinforces the other. This is to say that the tension exerted on the printing foils is divided between the two of them. As a result, in order to obtain a resistance against tearing which equals that of conventional foils having a thickness of 0.0035 inch, each of the foils according to this invention may have a thickness of only about 0.002 inch. It will be apparent that the double printing foils contemplated herein, when having a total thickness of 0.004 inch, composed of a thickness of 0.002 inch for each of the foils, includes up to four useful surfaces instead of two such surfaces of conventional double-sided printing plates. Accordingly, the volume to be stored, the shipping weight and the amount of material involved are reduced to 50% of that required in prior art printing foils.

When the plates are intended for use with printingv presses providedwith clamps ofanother type, the perforations may be omitted.

The invention will be further illustrated by reference to the accompanying drawing in which:

FIGURE 1 is an isometric view of a slightly unfolded double printing foil according to the invention, and

FIGURE 2 is a vertical section through the foil of FIG- URE 1 in a completely folded position.

Referring tothe drawing, a printing foil according to the invention consists essentially of a pair of foils 10 and 12 attached to each other along a common edge 14. The surfaces of foil 10 are designated 16 and 18, while numerals 20 and 22 indicate the surfaces of the foil 12. It has been found suitable to prepare at first a double sized, for example presensitized or otherwise processed sheet and bend it over along the center fold 14 to obtain the dual foil shown in FIGURE 1 in an isometric view. Any suitable base material but generally either aluminum foil or a paper base specially prepared in accordance with methods well known in the art may be used. Perforations for attaching the double foil to the cylinder of an offset printing press are arranged in two pairs of rows along two opposite edges and through both foils. The first pair of rows 2f perforations 24 run along the edge formed by the fold 14, whereby each of the perforations extends through both foils in such a manner that, when one foil is in surface contact with the other, the perforations appear in an aligned arrangement for securing the double foil to the press cylinder. Similarly, each of the edges 26 and 28 is provided with one row of perforations 30 and 32, respectively, in an identical arrangement.

It has been found suitable to provide the first mentioned rows of perforations 24 along the folded edge 14 and it is preferable to attach this edge to the hooks of the press cylinder which are positioned in the forward direction it is at this While it is, of course, possible to only process one Of the four surfaces, for example surface 16, preferably at least two of the surfaces are treated for imaging for thev purpose of making copies therefrom. In this case, it has been found suitable to fold the sheet in such-a manner that both useful surfaces 18 and 22 form the inner surfaces for additional protection against damage during 7 storage and shipping.

Since pretreatment for direct imaging and the presensitizing step is generally eifected before folding the sheet, as described above, it is then one continuing surface which -receives the 'direct image pretreatment or light-sensitive layer.

Upon folding, two adjacent useful surfaces are obtained which, protected initially as the inside surfaces 18 and 22, become the outer surfaces 16 and 20 only upon unfolding and bending over in the opposite direction. The

foregoing arrangement has been found especially useful in connection with presensitized paperbase foils. Generally, and specifically with aluminum foils, all four surfaces are processed, and when attaching the double foil to the press cylinder care must be taken that the specific surface from which prints are desiredfaces outwardly.

It will be obvious to those skilled in the art that many more modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all 'such modifications.

What is claimed is: V

1. A dual planographic printing foil for use in an offset printing press Which comprisesa pair of foils, having a combined thickness in the range of about 0.0035 to-0.0075 inch, attached along a common edge, each foil having two surfaces with an imageable layer on each, and means for attaching the dual foil to a printing cylinder.

2. A dual printing foil according to claim 1 made 'Of aluminum.

3.- A dual printing foil according to claim 1 made of 7 paper.

a 4; A dual printing foil according to claim 1 in which the means for attaching the dual foil are aligned apertures in the dual foil.

'Reierences Cited by the Examiner UNITED STATES PATENTS 7 1,140,877 5/ 15 Cocanari 9678 X 1,644,579 10/27 Lichtenstein 101-149.2

1,954,550 4/34 Weide. 2,060,190 11/36 Foster l0l--149.4 2,118,888 5/38 Lewis et al a. 101-149.4 2,147,778 7 2/39 Rubinstein '101-149,2 X 2,154,219 4/39 Shepherd l0l'149.2 2,185,188 1/40 Flanigan 101-4325 2,312,854 3/43 Toland'et a1. 2,567,435 9/51 Kraus. 2,684,922 7/54 Pollock et al. 3,010,394 11/61 Borchers et a1.

a I, FOREIGN PATENTS 720,249; 12/54 Great Britain. 1,146,906 5/57 France."

WILLIAM B. PENN, Primary Examiner.

ROBERT A. LEIGHEY, ROBERT E. PULFREY, Examiners. 

1. A DUAL PLANOGRAPHIC PRINTING FOIL FOR USE IN AN OFFSET PRINTING PRESS WHICH COMPRISES A PAIR OF FOILS, HAVING A COMBINED THICKNESS IN THE RANGE OF ABOUT 0.00035 TO 0.00075 INCH, ATTACHED ALONG A COMMON EDGE, EACH FOIL HAVING TWO SURFACES WITH AN IMAGEABLE LAYER ON EACH, AND MEANS FOR ATTACHING THE DUAL FOIL TO A PRINTING CYLINDER. 